Curable hydrophilic compositions

ABSTRACT

A curable composition is described, including a gel material derived from the curable composition, and medical articles including such material, wherein the transparent gel material includes a polymerized monofunctional poly(alkylene oxide) macromonomer component and a surface modified nanoparticle component.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/419,779, filed May 23, 2006, now allowed, the disclosure of which isincorporated by reference in its entirety herein.

BACKGROUND

The present invention is directed to curable hydrophilic compositions,gel materials comprising the cured hydrophilic compositions, and medicalarticles incorporating such materials, particularly medical articlesuseful as wound dressings. More particularly this invention is directedto curable hydrophilic compositions prepared from a monofunctionalpoly(alkylene oxide) macromonomer and surface modified nanoparticles.

Historically, exudate from a wound has been treated by absorbing itusing a dressing containing an absorbent material. Typical suchdressings contain a padded absorbent material attached to an adhesivetape backing The padded absorbent material is applied to the wound toabsorb the wound exudate. A difficulty with this type of dressing isthat the scab typically forms in and as part of the pad as the woundheals. Thus, when the dressing is removed, the scab is removed. Thisproblem has been addressed by providing a porous film between theabsorbent material and the wound to reduce the likelihood that a scabformed will become attached to the absorbent material.

More recently the use of so-called “occlusive” dressings for pressuresores and ulcers has gained increasing acceptance. A number of wounddressings of this kind are commercially available. Most of theseproducts are formed from several layers, including at least an innerskin-contacting layer and an outer backing layer. The dressing isapplied as a cover for the sore or ulcer in a size providing a marginaround the wound area that adhesively seals to the skin. The inner layercontains water-absorptive materials, so that fluid from the wound isabsorbed into the layer, making it possible to keep the dressing inplace for at least several days. Such occlusive dressings tend topromote healing by maintaining the wound under moist conditions withoutforming a crust, and serving as a barrier against bacterial infection.Such dressings for “moist wound healing” are particularly useful fordermal burns, traumatic skin deficiencies, incised wounds, and the like.

A wound care product in current use utilizes a hydrocolloid absorbent.Such a material typically has poor transparency so the treatment statecannot be observed from the outside. Also, such a material can partiallylose its integrity after absorbing wound fluid. Flexibility ofhydrocolloid dressings can be poor, which makes it difficult to applythe dressing to a bend portion of a body, such as a joint, etc. Theportion of the absorbent in contact with the wound is converted to agel-like material, and, when the dressing is removed, a portion of thisabsorbent material can be left in the wound, and must be removed topermit examination and/or before applying another dressing.

There are known hydrophilic gel materials useful in medical applicationssuch as wound dressings, however, many of them do not have theappropriate balance of absorption and cohesive strength often needed.Thus, additional such materials are needed. Furthermore, it be desirableto provide an occlusive material that is also transparent and flexiblefor use in a medical article such as a wound dressing or wound packingmaterial.

SUMMARY OF THE INVENTION

This invention provides curable hydrophilic compositions, polymeric gelmaterials comprising the cured compositions, and medical articlescomprising the gel materials for use therein, which are preferablyabsorbent, and more preferably absorbent and transparent.

The curable composition comprises:

-   -   a) 1 to 20 parts by weight of a surface modified nanoparticle        component having ethylenically unsaturated groups, wherein the        average particle size 20 nanometers or less; and    -   b) 80 to 99 parts by weight of a monomer component comprising:        -   a monofunctional poly(alkylene oxide) free-radically            polymerizable macromonomer having a poly(alkylene oxide)            moiety, optionally a multifunctional poly(alkylene oxide)            free-radically polymerizable macromonomer having a            poly(alkylene oxide) moiety, optionally a polar monomer, and            optionally a hydrophobic monomer.

The poly(alkylene oxide) moiety is of the general formula—(CH(R¹)—CH₂—O—)_(m)—(CH₂—CH₂—O—)_(n)—, wherein m may be 0, n is atleast 1 and the mole ratio of n to m (n:m) is greater than 2:1,preferably greater than 3:1; and R¹ is a (C₁-C₄) alkyl group. Thestructural distribution of —CH(R¹)—CH₂—O— moieties and —CH₂—CH₂—O—moieties may be random or blocks. Preferably m+n is at least 5, and morepreferably at least 10. Preferably m+n is less than 100, and morepreferably less than 50. It will be understood that m and n may benon-integral, as the poly(alkylene oxide) moieties are generally amixture of varying amounts or populations of the m and n units. Theethylenically unsaturated groups of the surface modified nanoparticlecomponent improves the physical properties of the resultant curedcomposition, particularly in the water-swollen state. The surfacemodified nanoparticles copolymerize with the monomer component improvingthe structural integrity of the cured composition. Preferably, thesurface modified nanoparticle component further comprises hydrophilicpoly(alkylene oxide) groups in addition to the ethylenically unsaturatedgroups, which allows the nanoparticles to be easily dispersed in themonomer component, while retaining the clarity (transparency).

The monomer component of the curable composition may further compriseother polar monomers (other than the monofunctional macromonomer),multifunctional poly(alkylene oxide), and/or free-radicallypolymerizable macromonomer (having two or more free-radicallypolymerizable groups) and/or hydrophobic monomers; each discussed inmore detail herein.

The present invention provides a medical article that includes a gelmaterial derived from the cured composition including a homopolymer orcopolymer of a monofunctional poly(alkylene oxide) free-radicallypolymerizable macromonomer having a poly(alkylene oxide) moiety.

By “gel” (or “polymer gel” or “polymeric gel material” or “hydrophilicgel”) it is meant a gel material, derived from the cured composition,capable of swelling on contact with water (or water-based fluids such asbody fluids including blood, plasma, and intracellular fluid or fluidssimilar to body fluids such as physiological saline), but does notdissolve in water. The gels are substantially continuous, i.e., lackinga cellular or void structure (although minor defects such as entrappedair bubbles or fractures may be present) and thus generally in a solidor semi-solid form. The term “gel” is used regardless of the state ofhydration. Preferably, the gel does not include water until it comes incontact with a surface from which it absorbs water (e.g., a wound).Significantly, even without water (or other plasticizing agents)preferred embodiments of the gel material of the present invention areflexible.

The application of water swelling polymer gels to medical practice is,for example, found in wound dressings, wound packings, adhesives(particularly pressure sensitive adhesives), contact lenses, intraocularlenses, adhesives for biological tissues, adhesion preventing materials,adsorbents for blood purification, base materials for releasingpharmacologic agents, and the like. Materials for dental moldings orimpressions are another potential medical article use. Thus, as usedherein, a “medical” application encompasses dental applications,including dental adhesives, restoratives, coatings, composites,sealants, etc. Because water swelling polymer gels have compositions andmechanical properties similar to those of biological tissues, such gelsmay be applied in a wide variety of fields in the future.

The present invention also provides a wound dressing that includes afacing layer (preferably, a fluid permeable facing layer) and a backinglayer (preferably, a moisture vapor permeable backing layer) with thegel material (typically in the form of a layer) disposed between thetwo. Preferably the backing layer is both moisture vapor permeable andliquid impermeable. The medical article, e.g., wound dressing, mayfurther include a layer of pressure sensitive adhesive to secure thearticle to the skin.

The composition of the present invention, which is absorbent andpreferably transparent, includes a surface modified nanoparticlecomponent having ethylenically unsaturated groups, and a polymerized,monofunctional, poly(alkylene oxide) macromonomer that, prior topolymerization, is free-radically polymerizable, monofunctional, and hasat least five —CH₂—CH₂—O— repeat units, and may have —CH(R¹)—CH₂—O—repeat units, such that the macromonomer has a total of at least five,and preferably at least ten repeat units, and the ratio of —CH₂—CH₂—O—repeat units to —CH(R¹)—CH₂—O— repeat units is at least 2:1.

This gel material can be a homopolymer of the monofunctionalmacromonomer, or it can be a copolymer (i.e., having two or moredifferent monomers), wherein at least one of the monomers is amonofunctional macromonomer of the above formula. Other monomers thatcan be copolymerized with the multifunctional macromonomer include, forexample, multifunctional poly(alkylene oxide) macromonomers, polarmonomers, and hydrophobic monomers.

By “absorbent” it is meant that the material is preferably capable ofabsorbing fluids, particularly body fluids and preferably moderate toheavy amounts of body fluids, while retaining its structural integrity(i.e., remaining sufficiently intact such that it can perform thefunction of acting as an absorbent moist wound healing dressing, forexample), and preferably its transparency. By “transparent” it is meantthat when the preferred material is applied to a patient (e.g., at awound site), the area underlying the dressing can be visualizedsufficiently to permit observation of the wound by a health care worker.

“(Meth)acryloyl” refers to both acryloyl and methacryloyl groups andincludes (meth)acrylates and (meth)acrylamides.

“Curable composition” refers to the total composition including themonomer component that comprises at least one polymerizablemonofunctional macromonomer and the inorganic surface-modifiednanoparticles.

The term “nanoparticles” is defined herein to mean particles (primaryparticles or associated primary particles) with a diameter less thanabout 100 nm, preferably 20 nanometers or less.

“Surface modified colloidal nanoparticle” refers to nanoparticles eachwith a modified surface such that the nanoparticles provide a stabledispersion.

“Agglomeration” refers to a weak association between primary particleswhich my be held together by charge or polarity and can be broken downinto smaller entities.

DETAILED DESCRIPTION

The present invention is directed to a curable composition comprising:

-   -   a) 1 to 20 parts by weight of a surface modified nanoparticle        component having ethylenically unsaturated groups and optional        hydrophilic poly(alkylene oxide) groups, wherein the average        particle size is 20 nanometers or less; and    -   b) 80 to 99 parts by weight of a monomer component comprising:        -   a monofunctional poly(alkylene oxide) free-radically            polymerizable macromonomer having a poly(alkylene oxide)            moiety, optionally a multifunctional poly(alkylene oxide)            free-radically polymerizable macromonomer having a            poly(alkylene oxide) moiety, optionally a polar monomer, and            optionally a hydrophobic monomer.

The gel material, derived from the cured composition of the presentinvention, can be used in medical articles. The gel material ishydrophilic and absorbent. Preferably, the gel material of the presentinvention is advantageously transparent, which allows for inspection ofan underlying material. Significantly, for medical articles,particularly wound dressings, this allows for visual inspection of thewound without removal of the wound dressing. More preferably, the gelmaterial is both absorbent and transparent.

Preferred medical articles, particularly wound dressings, of the presentinvention advantageously: can remove excess exudate from the wound;maintain a moist wound environment; allow gas exchange so that oxygen,water vapor, and carbon dioxide can pass through the article; arethermally insulating to maintain the wound at body temperature; may beimpermeable to liquids and microorganisms to minimize contamination andinfection; may be non-adherent to the wound so that no damage is done tothe granulating tissue; and minimize the need to cleanse the wound ofdressing material.

The cured composition is preferably absorbent in that it is capable ofabsorbing fluids, preferably moderate to heavy amounts of fluids such asbody fluids, while retaining its structural integrity (and preferablyits transparency). Preferably, herein, “absorbent” refers to a materialthat will absorb at least its own weight of an isotonic saline solution(0.9 wt-% sodium chloride in deionized water) after 24 hours at roomtemperature. That is, the material has an absorbency of at least 100%.More preferably, the gel material can absorb at least two times itsweight (200% absorbency), even more preferably at least four times itsweight (400% absorbency), and most preferably at least five times itsweight (500% absorbency) of an isotonic saline solution after 24 hoursat room temperature. Preferably, the gel material of the presentinvention is transparent whether dry or swollen with an aqueous solution(e.g., bodily fluid). Preferably, herein, transparent refers to amaterial having a total light transmittance of greater than 85% per ASTMD1003-00.

Preferred gel materials of the present invention may be relativelyflexible. Flexibility allows for a medical article incorporating the gelmaterial to be easily applied to a bend portion of a body, such as ajoint, etc. Nonflexible gel materials are also within the scope of thepresent invention. Such gel materials can be used as wound packingmaterials, for example.

The gel material of the present invention is also preferablybiocompatible. Herein, “biocompatible” means that the material can be incontact with bodily tissues (including fluids) without adversereactions. Typically, this occurs if the residual monomers used toprepare the polymer used in the gel material are present in less thanabout 1 percent by weight (wt-%) each, based on the total weight of thepolymer.

Preferably, the polymer used in the gel material of the presentinvention is inherently bacteriostatic and possesses low odor.Alternatively, bacteriostatic or odor removing agents can be added tothe polymer to enhance these properties of the gel material. Suchmaterials are described in greater detail below.

The curable composition of the invention comprises a surface modifiednanoparticle component having ethylenically unsaturated groups andoptional hydrophilic poly(alkylene oxide) groups wherein the averageparticle size is 20 nanometers or less, prior to surface modification.Preferably the polydispersity of the inorganic nanoparticles is lessthan 2, prior to surface modification.

Nanoparticles that are surface modified in accordance with the presentinvention comprise nanometer-sized, inorganic oxide particles such assilica; metal oxides such as alumina, tin oxide, iron oxide, zirconia,vanadia, and titania; combinations of these; and the like. The colloidalnanoparticles can comprise essentially a single oxide such as silica orcan comprise a core of an oxide of one type (or a core of a materialother than a metal oxide) on which is deposited an oxide of anothertype. Silica is the most preferred nanoparticle. It is also preferablethat the colloidal nanoparticles be relatively uniform in size andremain substantially non-aggregated, as nanoparticle aggregation canresult in precipitation, gellation, or a dramatic increase in viscosity.The term “nanometer-sized” refers to particles that are characterized byan average particle diameter in the range of from about 5 nm to about100 nm, but are preferably 20 nanometers or less, more preferably 10nanometers or less (prior to surface modification) in the curablecomposition of the invention. Further, the nanoparticles generally havea surface area greater than about 150 m²/gram, preferably greater than200 m²/gram, and more preferably greater than 400 m²/gram.

Average particle size of the inorganic nanoparticles can be measuredusing transmission electron microscopy. In the practice of the presentinvention, particle size may be determined using any suitable technique.Preferably, particle size refers to the number average particle size andis measured using an instrument that uses transmission electronmicroscopy or scanning electron microscopy. Another method to measureparticle size is dynamic light scattering that measures weight averageparticle size. One example of such an instrument found to be suitable isthe N4 PLUS SUB-MICRON PARTICLE ANALYZER available from Beckman CoulterInc. of Fullerton, Calif.

The unmodified nanoparticles may be provided as a sol rather than as apowder. Preferred sols generally contain from about 15 to about 50weight percent of colloidal inorganic oxide particles dispersed in afluid medium. Representative examples of suitable fluid media for thecolloidal particles include water, aqueous alcohol solutions, loweraliphatic alcohols, ethylene glycol, N,N-dimethylacetamide, formamide,and combinations thereof. The preferred fluid medium is aqueous, e.g.,water and optionally one or more alcohols. When the colloidal particlesare dispersed in an aqueous solvent, the particles may be stabilized dueto common electrical charges that develop on the surface of eachparticle. The common electrical charges tend to promote dispersionrather than agglomeration or aggregation, because the similarly chargedparticles repel one another. By contrast, fumed silica and silica gelsare aggregates of fused particles and thus will not as easily provide auniform dispersion of particles when combined with the monomer componentof the curable composition. Thus, a particularly desirable class ofnanoparticles for use in preparing the compositions of the inventionincludes sols of inorganic nanoparticles (e.g., colloidal dispersions ofinorganic nanoparticles in liquid media), especially sols of amorphoussilica.

Inorganic silica sols in aqueous media are well known in the art andavailable commercially. Silica sols in water or water-alcohol solutionsare available commercially under such trade names as LUDOX (manufacturedby E.I. duPont de Nemours and Co., Inc., Wilmington, Del., USA), NYACOL(available from Nyacol Co., Ashland, Mass.) or NALCO (manufactured byNalco Chemical Co., Oak Brook, Ill. USA). One useful silica sol is NALCO2326 available as a silica sol with mean particle size of 5 nanometers,pH 10.5, and solid content 15% by weight. Additional examples ofsuitable colloidal silicas are described in U.S. Pat. No. 5,126,394,incorporated herein by reference.

The sols used in the present invention generally may includecountercations, in order to counter the surface charge of the colloids.Depending upon pH and the kind of colloids being used, the surfacecharges on the colloids can be negative or positive. Thus, eithercations or anions are used as counter ions. Examples of cations suitablefor use as counter ions for negatively charged colloids include Na⁺, K⁺,Li⁺, a quaternary ammonium cation such as NR₄ ⁺, wherein each R may beany monovalent moiety, but is preferably H or lower alkyl such as CH₃—,combinations of these, and the like. Examples of counter anions suitablefor use as counter ions for positively charged colloids include nitrate,acetate, chloride, etc.

A variety of methods are available for modifying the surface ofnanoparticles including, e.g., adding a surface modifying agent tonanoparticles (e.g., in the form of a powder or a colloidal dispersion)and allowing the surface modifying agent to react with thenanoparticles. Other useful surface modification processes are describedin, e.g., U.S. Pat. No. 2,801,185 (Iler), U.S. Pat. No. 5,648,407 (Goetzet al.) and U.S. Pat. No. 4,522,958 (Das et al.), each incorporatedherein by reference.

Surface modifying agents that may be used to provide an ethylenicallyunsaturated group to the surface of the inorganic nanoparticles may berepresented by the formula X_(p)—R³—Y_(q) (I),

wherein:

X represents a functional group that may bond to, or associate with, thesurface of the inorganic nanoparticles, and is preferably selected froma silyl, hydroxyl, azido, mercapto, alkoxy, nitro, cyano, or aminogroup. Preferably X is a functional group that forms a covalent bondwith the surface functional groups of the inorganic nanoparticles, e.g.a reactive functional group that forms a covalent bond with the Si—OHgroups on the surface of silica nanoparticles.

R³ is a covalent bond or polyvalent hydrocarbon bridging group ofvalence p+q. In one embodiment R³ is a polyvalent hydrocarbon bridginggroup of about 1 to 20 carbon atoms, including alkylene and arylene andcombinations thereof, optionally including in the backbone 1 to 5moieties selected from the group consisting of —O—, —C(O)—, —S—, —SO₂—and —NR²— groups (an combinations thereof such as —C(O)—O—), wherein R²is hydrogen, or a C₁-C₄ alkyl group. In another embodiment, R³ is apoly(alkylene oxide) moiety. Preferably, R³ is a divalent alkylene.

Y is an ethylenically unsaturated polymerizable group, including vinyl,allyl, vinyloxy, allyloxy, and (meth)acryloyl,

and p and q are independently 1 to 4, preferably 1.

Preferred surface modifying agents include those with the followingformula:

Y—R³—Si—(OR⁴)_(b)(R⁴)_(3-b)   II

wherein:

R³ is a covalent bond or a polyvalent hydrocarbon bridging group ofvalence p+q. In one embodiment R³ is a polyvalent hydrocarbon bridginggroup of about 1 to 20 carbon atoms, including alkylene and arylene andcombinations thereof, optionally including in the backbone 1 to 5moieties selected from the group consisting of —O—, —C(O)—, —S—, —SO₂—and —NR²— groups (and combinations thereof such as —C(O)—O—), wherein R²is hydrogen, or a C₁-C₄ alkyl group. In another embodiment, R³ is apoly(alkylene oxide) moiety of the formula—(OCH₂CH₂—)_(n)(OCH₂CH(R¹))_(m)‘, where wherein n is at least 5, m maybe 0, and preferably at least 1, and the mole ratio of n:m is at least2:1 (preferably at least 3:1).

Preferably, R³ is a divalent alkylene.

Y is an ethylenically unsaturated polymerizable group, including vinyl,allyl, vinyloxy, allyloxy, and (meth)acryloyl,

R⁴ is independently an alkyl, aryl, or aralkyl group of 1 to 8 carbonatoms optionally substituted in available positions by oxygen, nitrogenand/or sulfur atoms; and b is 1 to 3.

Useful surface modifying agents that may be used to functionalize thenanoparticles with ethylenically unsaturated groups includesorganosilanes such as, for example,3-(methacryloyloxy)propyltrimethoxysilane,3-acryloxypropyltrimethoxysilane,3-(methacryloyloxy)propyltriethoxysilane,3-(methacryloyloxy)propylmethyldimethoxysilane,3-(acryloyloxypropyl)methyldimethoxysilane,3-(methacryloyloxy)propyldimethylethoxysilane,3-(methacryloyloxy)propyldiethylethoxysilane, vinyldimethylethoxysilane,vinylmethyldiethoxysilane, vinyltriacetoxysilane, vinyltriethoxysilane,vinyltriisopropoxysilane, vinyltrimethoxysilane, vinyltriphenoxysilane,vinyltri-t-butoxysilane, vinyltrisisobutoxysilane,vinyltriisopropenoxysilane, vinyltris(2-methoxyethoxy)silane, andmixtures thereof.

The ethylenically unsaturated surface modifying agent is used in amountssufficient to react with at least 10% of the available functional groupson the inorganic nanoparticle (for example the number of available Si—OHgroups on silica nanoparticles). The number of functional groups isexperimentally determined where a quantity of nanoparticles are reactedwith an excess of surface modifying agent so that all available reactivesites are functionalized with a coupling agent. Lower percentages offunctionalization may then be calculated from the result.

The multifunctionality of the surface modified nanoparticles leads tocrosslinking with the component monomers upon polymerization so that thenanoparticles are chemically bound to the cured composition. Typically,the higher the degree of functionalization, the higher the crosslinkdensity, leading to better mechanical properties. That is, the materialsof the present invention possess an advantageous balance of compliance(i.e., elasticity) and tensile strength as well as cohesive strength inthe swollen form as a result of the use of the ethylenically unsaturatedsurface modified functional groups.

The nanoparticles of the invention may be further modified to provide aplurality of hydrophilic poly(alkylene oxide) groups thereto. Thehydrophilic poly(alkylene oxide) groups comprise the moiety:

-Q-(CH(R¹)—CH₂—O—)_(m)—(CH₂—CH₂—O—)_(n)—R²   III

wherein n is at least 5, m may be 0, and preferably at least 1, and themole ratio of n:m is at least 2:1 (preferably at least 3:1);

Q is —O—, —S— or —NR²—, R¹ is a (C₁-C₄) alkyl group, which can be linearor branched, and R² is R¹ or H.

The distribution of the alkylene oxide moieties may be random (i.e.,there is a relatively random structural distribution of at least twodifferent moieties) or block.

In one embodiment, the nanoparticles may be functionalized by means of aambiphilic coupling agent capable of bonding a poly(alkylene oxide)compound to the nanoparticles.

The ambiphilic coupling agent has at least two reactive functionalgroups. The first reactive functional group is capable of covalentlybonding to the surface of the nanoparticles and the second reactivefunctional group is capable of bonding to the poly(alkylene oxide)compound. For example, reactive functionalities such as amino, hydroxyl,mercaptan, or isocyanate groups present on one component (thepoly(alkylene oxide) compound, coupling agent, or the particles) canreact with complementary reactive functionalities, such as oxirane,chloro-, bromo-, iodo-, alkyl, aziridine, anhydride, or isocyanatogroups, present on the other component (coupling agent or poly(alkyleneoxide) compound). More than one coupling agent may be used.

The poly(alkylene oxide) compound is of the formula

Z—(CH(R¹)—CH₂—O—)_(m)—(—CH₂—CH₂—O—)_(n)—R²   IV

wherein Z is a functional group, reactive with the second functionalgroup of the ambiphilic coupling agent, such as a hydroxyl, amino, thio,or isocyanate.

-   R¹ is a C₁ to C₄ alkyl group,

R² is a R¹ or H.

Preferably R¹ is a methyl and the poly(alkylene oxide) moiety is apoly(ethylene oxide-co-propylene oxide) where m and n are at least 1,m′+n is at least five, and n:m is at least 2:1. It will be understoodthat the poly(alkylene oxide) group may be random or block.

Useful ambiphilic silane coupling agents include those with thefollowing formula:

FG² _(a)-R³—Si—(OR⁴)_(b)(R⁴)_(3-b)   (V)

wherein:

FG² is the second reactive functional group of the ambiphilic couplingagent capable of reacting with complementary functionalities of the Zgroup of the poly(alkylene oxide) compound of Formula IV. Examples ofFG² include amino; hydroxyl; mercaptan; epoxy; chloro-, iodo-, andbromoalkyl; aziridine; cyclic carboxylic anhydride; hydrogen andisocyanato groups.

R³ is a covalent bond or a polyvalent hydrocarbon bridging group ofvalence p+q. In one embodiment R³ is a polyvalent hydrocarbon bridginggroup of about 1 to 20 carbon atoms, including alkylene and arylene andcombinations thereof, optionally including in the backbone 1 to 5moieties selected from the group consisting of —O—, —C(O)—, —S—, —SO₂—and —NR²— groups (an combinations thereof such as —C(O)—O—), wherein R²is hydrogen, or a C₁-C₄ alkyl group. In another embodiment, R³ is apoly(alkylene oxide) moiety of the formula—(OCH₂CH₂—)_(n)(OCH₂CH(R¹))_(m)—, where wherein n is at least 5, m maybe 0, and preferably at least 1, and the mole ratio of n:m is at least2:1 (preferably at least 3:1).

R⁴ is independently an alkyl, aryl, or aralkyl group of 1 to 8 carbonatoms optionally substituted by catenary oxygen, nitrogen and/or sulfuratoms;

-   a is 1 or 2; and-   b is 1 to 3;-   FG² and Z are generally selected so that one is nucleophilic and the    other is electrophilic. Examples of pairs of complementary, or    co-reactive, functional groups FG² and Z include isocyanate, epoxy    or anhydride groups with nucleophilic functional groups such as    hydroxyl, amino or mercapto. Alternatively, FG2 may be a hydrogen of    a silicon hydride, and Z may be a vinyl group.

It should be understood that when present in the compositions of theinvention the coupling agents may hydrolyze, in which case one or moreof the “OR⁴” groups will be converted to a silanol or silanolate.

Preferred ambiphilic silane coupling agents have the structureFG²-R³—Si(OR⁴)₃ wherein FG² is preferably an isocyanate group, and R³and R⁴ are as described above.

Additional information on ambifunctional silane coupling agents may befound in U.S. Pat. No. 5,204,219, issued to Van Ooij et al., U.S. Pat.No. 5,464,900, issued to Stofko et al., and U.S. Pat. No. 5,639,546,issued to Bilkadi and European Patent Application No. 0,372,756 A2.Alternatively the coupling agent can be a titanate or zirconatecompound, such as “Tyzor™ Titanate, 11 commercially available fromDuPont.

Alternatively, the poly(alkylene oxide) compound of the formula IV andthe ambiphilic coupling agent V are reacted together prior to surfacemodification of the inorganic nanoparticles. In this instance, thereaction may result in an PEG functionalized silane of the formula:

R²—(OCH₂CH₂—)_(n)(OCH₂CH(R¹))_(m)-Q′-R³—Si—(OR⁴)_(b)(R⁴)_(3-b)   (VI)

wherein Q′ is a divalent linking group resulting from the reactionbetween the “Z” group of the poly(alkylene oxide) compound of Formula IVand the “FG²” group of the ambiphilic silane coupling agent of FormulaV. For example, where FG²is an isocyanate and Z is a hydroxyl, Q′ willbe a urethane link.

R¹ is a C₁ to C₄ alkyl group,

R² is a R¹ or H,

R³ is a polyvalent hydrocarbon bridging group. In one embodiment R³ is apolyvalent hydrocarbon bridging group of about 1 to 20 carbon atoms,including alkylene and arylene and combinations thereof, optionallyincluding in the backbone 1 to 5 moieties selected from the groupconsisting of —O—, —C(O)—, —S—, —SO₂— and —NR²— groups (an combinationsthereof such as —C(O)—O—), wherein R² is hydrogen, or a C₁-C₄ alkylgroup. In another embodiment, R³ is a poly(alkylene oxide) moiety.Preferably, R³ is a divalent alkylene.

R⁴ is independently an alkyl, aryl, or aralkyl group of 1 to 8 carbonatoms optionally substituted by catenary oxygen, nitrogen and/or sulfuratoms;

n is at least 5, m may be 0, and preferably at least 1, and the moleratio of n:m is at least 2:1 (preferably at least 3:1); and

b is 1 to 3.

Less preferably the nanoparticles are first reacted with the ambiphiliccoupling agent of Formula V, then further reacted with the poly(alkyleneoxide) compound of Formula IV, as the efficiency of functionalization ofthe inorganic nanoparticles is reduced.

The ambiphilic coupling agent, whether the coupling agent V is used perse, or the poly(alkylene oxide) coupling agent (VI), is used in amountssufficient to react with all or part of the available surface functionalgroups on the inorganic nanoparticle, i.e those surface functionalgroups remaining after functionalization by the ethylenicallyunsaturated surface modifying agent of Formulas I or II. The number offunctional groups is experimentally determined where a quantity ofnanoparticles are reacted with an excess of coupling agent so that allavailable reactive sites are functionalized with a coupling agent. Lowerpercentages of functionalization may then be calculated from the result.The functionalization of the inorganic nanoparticles may be sequentialor concurrent. The inorganic nanoparticles may first be functionalizedby the surface modifying agent of Formulas I or II, followed byfunctionalization by surface modifying agents of Formulas V (followed byreaction with the compound of Formula IV), or the surface modifyingagent of Formula VI. Alternately the surface of the nanoparticles may besimultaneously modified by both the ethylenically unsaturated groups andthe poly(alkylene oxide) groups.

The monomer component of the instant curable composition comprises oneor more monofunctional poly(alkylene oxide) monomers to increase thehydrophilicity and absorbency of the cured composition used in formingthe gel material. The monomers comprise one terminal polymerizableethylenically unsaturated group (e.g., only one (meth)acryloyl group,vinyl group, allyl group or allyloxy group), a poly(alkylene oxide)moiety (such as previously described) and a second, non-polymerizable,terminal end group such as H, (C₁-C₄) alkoxy, aryloxy (e.g., phenoxy),or (C₁-C₄) alkaryloxy groups. These groups can be linear or branched.

Preferred monofunctional poly(alkylene oxide) monomers are of theformula:

R⁶-Q-(CH(R¹)—CH₂—O—)_(m)—(CH₂—CH₂—O—)_(n)—R²   VII

wherein

-   R⁶ is a ethylenically unsaturated polymerizable group, including    vinyl, allyl, vinyloxy, allyloxy, and (meth)acryloyl,-   R¹ is a (C₁-C₄) alkyl group,-   R² is H or R¹,-   Q is —O—, —S— or —NR²—,-   n is at least 5, m may be 0, and preferably at least 1, n+m is at    least 5 and preferably at least 10, and the mole ratio of n:m is at    least 2:1 (preferably at least 3:1).    Preferably R⁶ is selected from the groups consisting of:

wherein R² is H or C₁-C₄ alkyl,

-   R⁵ is an aromatic group, aliphatic group, alicyclic group, or    combinations thereof,-   W is an alkylene or alkylene oxide group, and r=2-10. Preferably R⁶    is (meth)acryloyl.

Examples of suitable monofunctional poly(alkylene oxide) monomersinclude poly(ethylene oxide)(meth)acrylate, poly(propyleneoxide)(meth)acrylate, poly(ethylene oxide-propyleneoxide)(meth)acrylate, and combinations thereof. Such monomers typicallyinclude nonreactive end groups (to free-radically polymerizations) suchas (C₁-C₄) alkoxy, aryloxy (e.g., phenoxy), (C₁-C₄) alkaryloxy,aryl(C₁-C₄) alkyloxy, or hydroxy groups. These groups can be linear orbranched. These monomers can be of a wide range of molecular weights andare commercially available from sources such as Sartomer Company, Exton,Pa.; Shinnakamura Chemical Co., Ltd., Tokyo, Japan; Aldrich, Milwaukee,Wis.; and Osaka Organic Chemical Ind., Ltd., Osaka, Japan.

The monofunctional macromonomers can be prepared, for example, byreacting monohydroxy terminated alkylene oxide homo- or copolymers(which are typically commercially available) with reactive ethylenicallyunsaturated compounds (e.g., acrylates).

A variety of reactive ethylenically unsaturated compounds such asacrylate derivatives can be used including, but not limited to,(meth)acrylic acid, (meth)acryloyl chloride, (meth)acrylic anhydride,and 2-isocyanatoethyl (meth)acrylate. In addition, the monohydroxyterminated alkylene oxide random copolymer can be reacted with adiisocyanate, such as isophorone diisocyanate, resulting in anisocyanate terminated functional random copolymer that is furtherreacted with either functional (meth)acrylates. Preferably, themonofunctional macromonomer is prepared by reacting the hydroxyterminated poly(alkylene oxide) compound with acrylic acid. Typically,if a stoichiometric amount of the ethylenically unsaturated reactant iscombined with the monohydroxy terminated alkylene oxide randomcopolymer, 100% conversion to the monosubstituted product is obtained.

The curable composition of the present invention optionally includes amultifunctional poly(alkylene oxide) free-radically polymerizablemacromonomer. The monomers comprise two or more terminal polymerizableethylenically unsaturated group (e.g., (meth)acryloyl group, vinylgroup, or allyl group), and a poly(alkylene oxide) moiety (as previouslydescribed). The multifunctional poly(alkylene oxide) macromonomerpreferably has a weight average molecular weight of at least about 2000.Preferably, the multifunctional poly(alkylene oxide) macromonomerincludes a alkylene oxide moiety of the formula—(CH(R¹)—CH₂—O—)_(m)—(CH₂—CH₂—O—)_(n)—, wherein m may be 0, n is atleast 1 and the mole ratio of n to m (n:m) is greater than 2:1,preferably greater than 3:1; and R¹ is a (C₁-C₄) alkyl group.

The multifunctionality of the material leads to crosslinking uponpolymerization. Typically, the higher the molecular weight, the greaterthe distance between crosslinks (i.e., the lower the crosslink density),which leads to better mechanical properties. That is, the materials ofthe present invention possess an advantageous balance of compliance(i.e., elasticity) and tensile strength as well as cohesive strength inthe swollen form as a result of the use of the multifunctionalpoly(alkylene oxide) macromonomer.

The multifunctional macromonomer preferably may have a weight averagemolecular weight of at least about 2000. Macromonomers with molecularweights lower than this tend to form brittle polymers. Preferably themultifunctional macromonomer has a weight average molecular weight of atleast about 4000, more preferably at least about 6000, and mostpreferably at least about 10,000. Such materials can have significantlyhigher molecular weights as well. Preferably, such multifunctionalmacromonomers have a molecular weight such that they are flowable andprocessable at room temperature. High molecular weight multifunctionalmacromonomers that are not flowable at room temperature can be used ifthey can be processed using diluents or other additives and/or highertemperatures (e.g., extrusion temperatures). Most preferably, usefulmultifunctional macromonomers are liquid at room temperature.

Herein, multifunctional means that the macromonomer has more than onereactive group that is free radically polymerizable. Preferably, thereare two or three reactive groups, and more preferably two reactivegroups. Such multifunctional macromonomers can be linear or branched,preferably they are linear.

Preferably, the free radically polymerizable functionality of themultifunctional macromonomer includes ethylenic unsaturation. Examplesof suitable ethylenically unsaturated groups include (meth)acryloyl,(meth)acrylamido, allyloxy, vinyl, etc., as well as combinationsthereof.

Preferably, the multifunctional macromonomer is difunctional. Aparticularly preferred difunctional macromonomer is of the formula(Formula VIII):

R⁶-Q-(CH(R¹)—CH₂—O—)_(m)—(CH₂—CH₂—O)_(n)—R⁷   VIII

wherein:

-   R⁶ and R⁷ are each independently an ethylenically unsaturated    polymerizable group, including vinyl, allyl, vinyloxy, allyloxy, and    (meth)acryloyl,-   R¹ is a (C₁-C₄) alkyl group,-   R² is H or R¹,-   Q is —O—, —S— or —NR²—,-   n is at least 5, m may be 0, and preferably at least 1, n+m is at    least 5, and preferably at least 10, and the mole ratio of n:m is at    least 2:1 (preferably at least 3:1).

Preferably R⁶ and R⁷ are each independently selected from the groupsconsisting of

wherein

-   R¹ is a C₁ to C₄ alkyl,-   R² is H or R¹,-   R⁵ is an aromatic group, aliphatic group, alicyclic group, or    combinations thereof,-   W is an alkylene or alkylene oxide group, and r=2-10. Preferably R⁶    and R⁷ are (meth)acryloyl.

Preferably, the R⁵ groups are derived from diisocyanates. Morepreferably, R⁵ is selected from the group consisting of —(CH₂)o- whereino=1-18, tolylene, and

Most preferably, R⁵ is derived from toluene diisocyanate, hexamethylenediisocyanate, or H₁₂-MDI (4,4′-methylene bis(cyclohexyl)diisocyanate).

Preferably, W is a C₂ to C₂₀ alkylene or a poly(alkylene oxide) moietyof of the general formula —(CH(R¹)—CH₂—O—)_(m)—(CH₂—CH₂—O—)_(n)—,wherein m may be 0, n is at least 1 and the mole ratio of n to m (n:m)is greater than 2:1, preferably greater than 3:1; and R¹ is a (C₁-C₄)alkyl group. The poly(alkylene oxide) moieties of Formula VII may berandom or block. More preferably, it is a random poly(ethyleneoxide-co-propylene oxide)-containing multifunctional macromonomer.

The multifunctional macromonomers can also be tri-, tetra-,penta-functional, etc., macromonomers. Such compounds also include apoly(alkylene oxide) moiety of Formula I, wherein n is at least 5, m is0 and preferably at least 1, m+n is at least 5 and preferably at least10, and the ratio of n to m is at least 2:1, preferably at least 3:1;and R¹ is a methyl group, and two or more end groups selected from thelist of R⁶ and R⁷ groups above. It should be understood that such endgroups may be bonded through oxygen or nitrogen.

Multifunctional macromonomers can be linear with branched end groups orcan be branched through a central core. Branched macromonomers can beprepared, for example, by chemical modification of linear diamino- ordihydroxy terminated alkylene oxide random copolymers to producemultiple reactive end groups at each chain end. For example, amacromonomer with two polymerizable groups at each chain end can beprepared by reacting a linear diamino- or dihydroxy terminatedpoly(alkylene oxide) compound with trimellityl chloride followed byreaction with 2-hydroxyethyl methacrylate. Branch points in themacromonomer can also be introduced through incorporation of a centralcore. Examples of such materials include, but are not limited to,ethoxylated/propoxylated dipentaerythritol, pentaerythritol, andtrimethyolpropane that have been further reacted with reactiveethylenically unsaturated compounds.

It should also be understood that each arm of a multifunctionalmacromonomer includes the copolymeric random alkylene oxide moiety,although each arm in any one macromonomer can be different. Also, therecan be other groups or linkages, such as urethanes and/or urea groupsbetween various copolymeric random alkylene oxide moieties in any onearm.

The multifunctional macromonomers can be prepared, for example, byreacting diamino- or dihydroxy-terminated poly(alkylene oxide) compound(which are typically commercially available such as poly(ethyleneoxide-co-propylene oxide) commercially available as UCON-75H-90,000 fromDow Chemical Co., Midland, Mich.) with reactive ethylenicallyunsaturated compounds (e.g., acrylates). A variety of reactiveethylenically unsaturated compounds such as acrylate derivatives can beused including, but not limited to, (meth)acrylic acid, (meth)acryloylchloride, (meth)acrylic anhydride, and 2-isocyanatoethyl(meth)acrylate.In addition, the diamino- or dihydroxy-terminated poly(alkylene oxide)compound can be reacted with a diisocyanate, such as isophoronediisocyanate, resulting in an isocyanate terminated functional randomcopolymer that is further reacted with either functional(meth)acrylates.

Preferably, the functional macromonomer is prepared by reacting thediamino- or dihydroxy-terminated poly(alkylene oxide) compound withmethacrylic anhydride. Typically, if a stoichiometric amount of theethylenically unsaturated reactant is combined with the diamino- ordihydroxy terminated poly(alkylene oxide) compound, 100% conversion tothe disubstituted product is obtained. However, if less than astoichiometric amount is used, the product is typically a mixture ofdisubstituted and monosubstituted products and possibly some diamino- ordihydroxy terminated starting material. Such mixtures tend to providegels with higher absorbency.

A multifunctional macromonomer as described herein can be copolymerizedwith the monofunctional macromonomers or other hydrophilic monomers toenhance the absorbency of the polymer used in forming the gel material.Examples of suitable hydrophilic monomers include monofunctionalpoly(alkylene oxide) monomers and other polar monomers. Themultifunctional macromonomer (or combination of macromonomers) can becopolymerized with hydrophobic monomers also to better control theabsorbency of the polymer. Combinations of such hydrophilic andhydrophobic monomers can be used if desired.

Polar monomers other than the mono- and multifunctional poly(alkyleneoxide) macromonomers can also be used to increase the absorbency of thepolymer used in forming the gel material. Preferred polar monomers canalso provide compliance to the resultant polymer. Examples of suitablepolar monomers include 2-hydroxyethyl(meth)acrylate (HEMA),2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate,4-hydroxybutyl(meth)acrylate, N-vinyl caprolactam, N-vinyl acetamide,N-vinyl pyrrolidone, acrylamide, mono- or di-N-alkyl substitutedacrylamide, (meth)acrylic acid, itaconic acid, beta-carboxyethylacrylate, glycerol methacrylate,[2-(meth)(acryloyloxy)ethyl]trimethylammonium chloride,[2-(meth)(acryloyloxy)ethyl]trimethylammonium methyl sulfate, andcombinations thereof. Preferred polar monomers include2-hydroxyethyl(meth)acrylate (HEMA) and N-vinyl pyrrolidone.

Hydrophobic monomers can be used to reduce (and thereby better control)the absorbency of the polymer used in forming the gel material, andpreferably improve the strength of the polymer. Examples of suitablehydrophobic monomers include (meth)acrylic acid esters such as laurylacrylate, 2-ethylhexyl acrylate, and isooctyl acrylate, as well asalpha-methylstyrene, and combinations thereof.

Monomers used in forming the monomer component of the present inventionpreferably include no greater than about 80 wt-% of a monofunctionalpoly(alkylene oxide) monomer, based on the total weight of the monomercomponent. More preferably, the monofunctional poly(alkylene oxide)monomer is used in an amount of at least about 30 wt-%, based on thetotal weight of the polymer. Most preferably, the monofunctionalpoly(alkylene oxide) monomer is used in an amount of at least about 40wt-%, based on the total weight of the polymer.

Monomers used in forming the monomer component of the present inventionmay include at least about 0.1 wt-% of the optional multifunctionalpoly(alkylene oxide) macromonomer, based on the total weight of themonomer component. Preferably, the monomer component include at leastabout 5 wt-% of the multifunctional poly(alkylene oxide) macromonomer,based on the total weight of the polymer. More preferably, themultifunctional poly(alkylene oxide) macromonomer is used in an amountof no greater than about 20 wt-%, based on the total weight of themonomer component.

Preferred monomers used in forming the monomer component of the presentinvention include no greater than about 40 wt-% of an optional polarmonomer, based on the total weight of the monomer component. Morepreferably, the polar monomer is used in an amount of no greater thanabout 35 wt-%, based on the total weight of the monomer component. Mostpreferably, the polar monomer is used in an amount of no greater thanabout 30 wt-%, based on the total weight of the monomer component.Preferably, the polar monomer is used in an amount of at least about 5wt-%, based on the total weight of the monomer component. Morepreferably, the polar monomer is used in an amount of at least about 10wt-%, based on the total weight of the monomer component.

Preferred monomers used in forming the monomer component of the presentinvention include no greater than about 20 wt-% of an optionalhydrophobic monomer, based on the total weight of the monomer component.More preferably, the hydrophobic monomer is used in an amount of lessthan 20 wt-%, based on the total weight of the monomer component. Evenmore preferably, the hydrophobic monomer is used in an amount of nogreater than about 10 wt-%, based on the total weight of the monomercomponent. Most preferably, the hydrophobic monomer is used in an amountof no greater than about 5 wt-%, based on the total weight of themonomer component.

The monomers used in forming the monomer component of the presentinvention are preferably substantially acid free. By this it is meantthat no acidic monomers (e.g., (meth)acrylic acid, itaconic acid) areused in preparing the polymer in the gel material, although there may becertain acidic monomers present as contaminants in other monomers used.Thus, “substantially acid free” means that less than about 2 wt-% of themonomers used to prepare the polymer are acidic monomers.

The curable composition of the present invention may be prepared bycombining the surface modified inorganic nanoparticle component and themonomer component. The components, including the component monomers andthe surface modified nanoparticle component, may be combined in anyorder. Generally the inorganic nanoparticles are surface modified, thencombined with the monomer component rather than modifying the inorganicnanoparticles in situ.

It has been found that modifying the inorganic nanoparticles withpoly(alkylene oxide) groups (in addition to the ethylenicallyunsaturated groups) prior to combining with the monomer componentimproves the compatibility and resultant transparency of the curablecomposition and gels. In the absence of poly(alkylene oxide) surfacemodifying groups on the surface of the inorganic nanoparticles, it ispreferred to combine the surface modified nanoparticle component and thepolar monomer prior to addition of the monofunctional macromonomer andmultifunctional macromonomer. First combining the surface modifiednanoparticle component and the monofunctional macromonomer may lead tocloudiness and reduced transparency, and is therefore less preferred.

The gel, or cured compositions, may be produced by polymerizing theabove-described components (I.e. the surface modified nanoparticlecomponent and the mononomer component) by conventional polymerizationmethods. Typical polymerization methods that can be used include thermaland/or photochemical as well as bulk and solution polymerization.

In a typical solution polymerization method, a monomer component andsurface modified nanoparticle component are heated with stirring in thepresence of a solvent and a polymerization initiator. Examples of thesolvent are methanol, ethanol, isopropanol, acetone, methyl ethylketone, methyl acetate, ethyl acetate, toluene, xylene, and an ethyleneglycol alkyl ether. Those solvents can be used alone or as mixturesthereof. Examples of the polymerization initiator are benzoyl peroxide,cumene hydroperoxide, diisopropyl peroxydicarbonate, andazobisisobutyronitrile. Those polymerization initiators can be usedalone or as mixtures thereof.

In a typical photopolymerization method, a mixture of the monomercomponent and surface modified nanoparticle component is irradiated withultraviolet (UV) rays in the presence of a photopolymerization initiator(i.e., photoinitiators). Preferred photoinitiators are those availableunder the trade designations IRGACURE from Ciba Speciality ChemicalCorp., Tarrytown, N.Y. and include 1-hydroxy cyclohexyl phenyl ketone(IRGACURE 184), 2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651),bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide (IRGACURE 819),1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one(IRGACURE 2959), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone(IRGACURE 369),2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IRGACURE907), and 2-hydroxy-2-methyl-1-phenyl propan-1-one (IRGACURE 1173).Particularly preferred photoinitiators are IRGACURE 819 and 2959.

A particularly preferred method of forming the cured composition isdescribed in U.S. Pat. No. 6,960,275 (Vesley et al.).

Preferably, the method involves a “syrup polymer” technique, by whichthe monofunctional macromonomer and surface modified nanoparticlecomponent are dissolved or dispersed in the component monomers, whichreact into the polymer backbone, further increasing the molecularweight. Molecular weight may be controlled through the use of chaintransfer agents and chain retarding agents, as are known in the art,such as alkyl mercaptans such as dodecyl mercaptan, isooctylthioglycolate, and alpha-methylstyrene.

Thus, the present invention also provides a syrup polymer mixture andthe polymerized product thereof. The syrup polymer mixture comprises 1to 20, preferably 1 to 10 parts by weight of a surface modifiednanoparticle component and 80 to 99 parts, preferably 90 to 99 parts byweight of a monomer mixture comprising: 30 to about 80 wt-% of amonofunctional poly(alkylene oxide) monomer; 0 to about 40 wt-% of apolar monomer (distinct from the monofunctional poly(alkylene oxide)monomer); 0 to about 20 wt-% of a hydrophobic monomer: about 0 wt-% to20 wt-% of a multifunctional poly(alkylene oxide) macromonomer. Such asyrup is preferably partially polymerized (typically, about 10-15%conversion) to form a coatable composition (typically, having aviscosity of about 300 centipoise to about 20,000 centipoise), thencoated onto a backing or a release liner, for example, and thenpolymerized further to form a gel. The syrup polymer mixture preferablyincludes a photoinitiator. The step of forming a gel from the syruppolymer mixture preferably includes applying radiation (infrared,ultraviolet, visible, electron beam, etc., preferably, ultravioletradiation), thermal energy, or a combination thereof (preferablysequentially).

The gel material, derived from the cured composition of the presentinvention, can include one or more active agents, such aspharmacologically active agents. Examples include, but are not limitedto, growth factors (e.g., TGF, FGF, PDGF, EGF, etc.), antibacterialagents (e.g., penicillins, neomycin sulfate, sulphonamides,sulfadiazine, silver sulfadiazine, trimethoprim, and other antibiotics,as well as povidone iodine, iodine, silver, silver chloride, andchlorhexidine), antifungal agents (e.g., griseofulvin, chlormidazolehydrochloride, clotrimazole, ketoconazole, miconazole, miconazolenitrate, nistatin, and tolnaftate), disinfectants and antiseptics (e.g.,benzalkonium chloride, cetalkonium chloride, chlorhexidine gluconate,ethanol, iodine, methylbenzethonium, povidone iodine, isopropanol,silver, silver oxide, silver salts such as silver lactate and silverchloride, triclosan), local anaesthetics (e.g., tetracaine, benzocaine,prilocaine, procaine), debriding agents, anti-inflammatory agents (e.g.,indomethacin, ketoprofen, dichlofenac, ibuprofen, etc.), astringents,enzymes, nutrients (e.g., vitamins, minerals, oxygen, etc.), drugs forcataplasms (e.g., menthol, camphor, peppermint, capsicum extract,capsaicin, etc.), and odor absorbing agents (e.g., zeolites, silicates,chitosans, cyclodextrins, etc.). Preferred active agents areantibacterial agents such as povidone iodine, iodine, silver, silverchloride, and chlorhexidine. Active agents can be used alone or asmixtures thereof. They can be added before or after the reaction productof this invention is cured as long as they do not interfere withpolymerization of the polymer. Preferably, they are added in an amountor manner that does not interfere with the function or clarity of thefinished gel material.

Optionally, the gel material can include hydrocolloids, typically in theform of particles, although they are not necessarily preferred sincethey can diminish the transparency of the gel material. Examples ofhydrocolloids include, but are not limited to, natural gums, such asplant exudates (gum arabic, ghatti, karaya, and tragacanth); plant seedgums (guar, locust bean and acacia), seaweed extracts (agar, algin,alginate salts and carrageenin), cereal gums (starches and modifiedstarches), fermentation or microbial gums (dextran and xanthan gum),modified celluloses (hydroxymethylcellulose, microcrystalline celluloseand carboxymethylcellulose) pectin, gelatin, casein and synthetic gums(polyvinylpyrrolidone, low methoxyl pectin, propyleneglycol alginates,carboxymethyl locust bean gum and carboxymethyl guar gum) and likewater-swellable or hydratable hydrocolloids. The term hydrocolloid isused regardless of the state of hydration. The gel material of thepresent invention preferably includes an amount of the hydrocolloid suchthat the material is transparent (preferably, the total lighttransmittance is greater than 85% per ASTM D1003-00). Typically, theamount of hydrocolloid, if used, is less than about 5 wt-%, based on thetotal weight of the gel material.

Other additives that can be incorporated into the cured compositioninclude: viscosity modifiers (e.g., polymeric thickeners such as thatcommercially available under the trade designation GANTREZ resin fromInternational Specialty Products, Wayne, N.J.); chain transfer orretarding agents (e.g., such as alkyl mercaptans such as dodecylmercaptan, isooctyl thioglycolate, and a-methylstyrene, the latter ofwhich can also be a hydrophobic monomer as discussed above); colorants;indicators; tackifiers; plasticizers (e.g., water, glycerin,polyethylene oxide, polypropylene oxide, and mixtures thereof such asthose commercially available under the trade designation PLURONICS fromBASF Co., as well as various low molecular compounds capable ofplasticizing the polymer); antioxidants; etc. Such additives can beadded either before or after the polymerization using techniques knownto one of skill in the art. Preferably, if used, they can be added in anamount and manner that does not interfere with the function or clarityof the gel material.

Preferably, the cured composition is substantially free of plasticizers,including water. This is advantageous at least because special packagingis not required. Furthermore, plasticizers can migrate to other parts ofa dressing, for example, which can be detrimental to the integrity ofthe dressing, or into the body of the patient on which the dressing isdisposed.

Optionally, the gel material, derived from the cured composition, mayhave a patterned surface on at least one major surface thereof. Thepatterned surface allows greater surface area for absorption of woundexudate when oriented toward the wound surface, while reducing theabsorbent surface area in direct or indirect contact with the wound.More significantly, the patterned surface reduces the propensity of theabsorbent layer to swell and push against the wound, avoids mushrooming(i.e. expansion of the gel layer through a porous film) and furtheravoids premature separation of an adhesive layer from the skin.

The optional pattern imparted to the surface of a layer of the gelmaterial may be any suitable preselected three-dimensional pattern.Preferably, the pattern is one that increases the surface area availablefor absorption and reduces swelling into the wound, retards mushrooming,and/or enhances integrity of the material upon hydration. The patterncan include an array of pattern elements that include, but are notlimited to, ridges, channels, mounds, peaks, hemispheres, pyramids,cylinders, cones, blocks, and truncated variations and combinationsthereof. The pattern may further include apertures having apredetermined shape and size extending through the thickness of theabsorbent layer.

The specific pattern element is advantageously chosen to present minimalsurface area in contact with a wound or the facing film if present. Theminimal surface area further retards the tendency of the gel material toswell into the wound, mushroom, or adhere to the wound site. Especiallyuseful elements include pyramids, cones and truncated versions thereof,and ridges that are triangular in cross section. The elements may berandom or non-random in the x direction, the y direction, or both. Forease of manufacture, it is preferable that the pattern comprises anon-random array of elements disposed on the surface of the gel.

If desired, a pattern may also be imparted to the outer face of the gellayer (i.e., the major surface of the gel layer that faces away from thewound surface). Imparting such a pattern increases the surface area ofthe gel layer and may promote greater evaporation of the fluid from thegel material. The pattern may be the same or different than the patternon the facing surface of the gel material, as can the size of thepattern elements. Further, the individual elements on either surface ofthe gel material may be protuberances extending form the surface, or maybe depressions in the surface.

If desired, the gel material may be in direct contact with the woundand/or skin surface. However, direct contact may be provided by othersuitable hydrocolloid and hydrogel absorbent materials.

In a preferred medical article, the gel material forms a layer that isgenerally about 250 micrometers (i.e., microns) to about 5000micrometers in total thickness.

Optionally, a wound dressing of the invention may include at least twoabsorbent layers: a first absorbent layer and a second absorbent layer.The first absorbent layer is typically more absorbent than the secondabsorbent layer, and can retain a greater volume of body fluids than thesecond absorbent layer. The second absorbent layer is positioned suchthat it is located between the first absorbent layer and the wound. Thissecond absorbent layer provides integrity to the wound dressing andavoids transfer of the first absorbent layer into the wound.

The first absorbent layer typically contains the polymer described aboveprepared from the multifunctional macromonomer. The second absorbentlayer is typically positioned in contact with the first absorbent layerand is typically less absorbent of body fluids than the first absorbentlayer. The second absorbent layer can contain the reaction product of anacrylic acid ester of a non-tertiary alcohol having from 4 to 14 carbonatoms; a hydrophilic, ethylenically unsaturated monomer; and a polar,ethylenically unsaturated monomer, although other compositions can beused in the second absorbent layer. Generally, the second absorbentlayer functions as a “barrier” between the first absorbent layer (whichmay partially “disintegrate” when exudate is unevenly, rapidly absorbedor when it absorbs more than about 500%) and the wound. Preferably thesecond absorbent layer has adhesive properties (or is a pressuresensitive adhesive) and functions to enhance the overall integrity ofthe wound dressing. In this regard, the second absorbent layer ties thefirst absorbent layer to a wound-facing layer (or to the wound itself).By having adhesive properties, this second absorbent layer not only aidsin controlling the absorption of exudate, but also physically joinsother components of the dressing.

As stated above, the first absorbent layer is typically significantlymore absorbent than the second absorbent layer, and preferably has anabsorbency at least 100 percent greater than the absorbency of thesecond absorbent layer. The first absorbent layer preferably absorbs atleast 400 percent of its weight after immersion in an isotonic salinesolution after 24 hours at room temperature.

A typical wound dressing of the present invention preferably includes aporous or non-porous facing layer to provide a fluid permeable barrierbetween the wound site and the gel layer. The facing layer allowstransport of moisture (i.e. fluid and vapor) from the wound to the gellayer and may isolate the wound from other components of the dressing.The facing layer is preferably soft, flexible, conformable,non-irritating and non-sensitizing. Any of a variety of polymers may beused including polyurethane, polyethylene, polypropylene, polyamide orpolyester materials. Further, the facing layer may be in the form ofmoisture vapor permeable films, perforated films, woven-, non-woven orknit webs or scrims. A preferred facing layer comprises a polyurethanefilm.

In one useful embodiment, the facing layer is conformable to animal(including human) anatomical surfaces, has a moisture vapor transmissionrate (MVTR) of at least 300 grams per square meter per 24 hours at 80%relative humidity differential at 40° C. (per method of Chen, U.S. Pat.No. 5,733,570), is impermeable to liquid water throughout substantiallyits entire imperforate area and contains perforations means for passingwound exudate through the facing layer. This means that the facing layerdoes not pass liquid water under normal wound treatment conditionsexcept at the places in the facing layer that are positively perforatedto allow the exudate to pass into the reservoir.

The preferred moisture vapor transmission rate of the facing layer is atleast 600 grams per square meter per 24 hours at an 80% relativehumidity differential at 40° C. The facing layer may further comprise apressure sensitive adhesive layer. The adhesive coated facing layerpreferably has the aforesaid MVTR. Therefore, if the facing layer isimpermeable to liquid water except for the perforation means, theadhesive can be permeable to liquid water and vice versa. Porous ornon-porous facing layers such as perforated polyamide, polyester,polypropylene, polyethylene, polyether-amide, polyurethanes, chlorinatedpolyethylene, styrene/butadiene block copolymers (KRATON brandthermoplastic rubber, Shell Chemical Company, Houston, Tex.) andpoly(vinyl chloride) and those described in U.S. Pat. No. 3,121,021(Copeland) that are covered with a pressure sensitive adhesive that isnot permeable to liquid water can be used for the facing layer.Optionally these films can be perforated. Additional porous materialsinclude woven and non-woven substrates.

It is preferred that the facing layer have the above mentioned moisturevapor or liquid permeability (1) so that maceration of the skin underthe wound dressing does not occur, (2) so that moisture build-up underthe facing layer does not cause the facing layer and, therefore, wounddressing to be lifted off the skin, and (3) to enhance proximation ofthe wound edges. Preferred facing layers are thin polymeric filmsoptionally coated with pressure sensitive adhesive which, incombination, have the above characteristics.

The perforation means in the facing layer are holes or slits or otherperforations that conduct the passage of liquid water or wound exudatefrom the wound into the absorbent layer of the wound dressing. Theperforations may additionally extend through an adhesive layer, if thefront surface of the facing film (that surface facing toward the wound)is coated with a pressure sensitive adhesive layer.

A backing layer may be present in all of the embodiments of the presentinvention. Preferably the backing layer is conformable to animalanatomical surfaces, impermeable to liquid water and has a moisturevapor transmission rate of at least 600 grams per square meter per 24hours at an 80% relative humidity differential at 40° C. The backinglayer, in combination with a facing layer, may be constructed to form areservoir (e.g., a pouch or envelope) that surrounds the gel layer, intowhich the exudate from the wound passes. This reservoir does not permitliquid water or exudate to pass out of it. Instead, the gel layerabsorbs the exudate, and moisture in the exudate passes through thebacking layer in a vapor form into the atmosphere. The reservoirdressing permits wound exudate to be rapidly removed from the wound siteand prevents liquids or bacteria from outside the dressing tocontaminate the wound site.

In order to remove moisture vapor, the moisture vapor transmission rateof the backing layer is at least as above noted, and preferably at least1200 grams per square meter per 24 hours at an 80% relative humiditydifferential at 40° C.

The preferred embodiments for the facing and backing layers are thinconformable polymeric films. Generally the films are about 12 microns toabout 50 microns in thickness, preferably about 12 microns to about 25microns. Conformability is somewhat dependent on thickness, thus thethinner the film the more conformable the film. Reference has been madeherein to the films utilized in the medical article (e.g., wounddressing) of the present invention being conformable to animalanatomical surfaces. This means that when the films of the presentinvention are applied to an animal anatomical surface, they conform tothe surface even when the surface is moved. The preferred films areconformable to animal anatomical joints. When the joint is flexed andthen returned to its unflexed position, the film stretches toaccommodate the flexation of the joint but is resilient enough tocontinue to conform to the joint when the joint is returned to itsunflexed condition.

Examples of films which are useful in applicant's invention as facing orbacking layers include polyurethanes such as those available under thetrade designation ESTANE from B.F. Goodrich, Cleveland, Ohio,elastomeric polyester such as those available under the tradedesignation HYTREL from E.I. duPont deNemours & Co., Wilmington, Del.,blends of polyurethanes and polyesters, polyvinyl chlorides, andpolyether-amide block copolymers such as those available under the tradedesignation PEBAX available from Elf-Atochem. Particularly preferredfilms for use in the present invention are polyurethane and elastomericpolyester films. The polyurethane and elastomeric polyester filmsexhibit a resilient property that allows the films to have goodconformability. Particularly useful films include “spyrosorbent” filmshaving a differential moisture vapor transmission rate (MVTR). Dressingsincorporating spyrosorbent films not only manage wound exudate byabsorption, but have the ability to adjust the moisture vaportransmission properties in response to the amount of exudate. Suchspyrosorbent films are hydrophilic, moisture vapor permeable and have arelatively high MVTR (wet), and have a differential MVTR ratio (wet todry) that is greater than 1, and preferably greater than 3:1. The dryMVTR is greater than about 2600 g/m²/24 hrs, preferably about 3000 to4000 g/m²/24 hrs. A particularly preferred spyrosorbent film, useful asa backing layer, is a segmented polyurethane such as a segmentedpolyether polyurethane urea based on polytetramethylene glycol andpolyethylene glycol polyols. Such a spyrosorbent films are described inU.S. Pat. Nos. 5,653,699 and 4,849,458 (Reed et al.).

Another suitable backing layer is a fluid control film having at leastone microstructures-bearing surface with channels that permitdirectional control of a liquid. This film can be used to transport afluid to a remote site and thereby facilitate wicking away of a fluid(e.g., wound exudate). Such a film is disclosed in InternationalPublication No. WO 00/42958.

Many different constructions of a wound dressing are possible with thefacing layer, the gel layer, and the backing layer. In one embodiment,the areas of the facing layer and the backing layer are greater thanthat of the gel layer and the facing layer is bonded to the backinglayer, thereby forming a pouch, with the gel disposed between the two.In another embodiment, one of the facing or backing layers may besubstantially the same area as the gel layer, and the other of greaterarea. The greater area of the facing or backing layer forms a peripheryto which an adhesive layer and a release liner may be attached. It willfurther be understood that the facing and/or backing layer may beattached or bonded to the adjacent surface of the gel layer to form acontiguous layer construction, in which the backing and facing layersmay be the same or of greater area than the gel layer. Alternatively,the backing and facing layers may be bonded to each other, and may ormay not be bonded to the gel layer. In these last constructions, the gellayer is constrained within a pouch created by the attachment of thefacing and backing layers to each other. The layers may be bonded toeach other by any conventional means such as adhesives, heat sealing, orother bonding means.

It is preferred that the facing and backing layers of the medicalarticles of the present invention be at least translucent and morepreferably sufficiently transparent so that the wound site to which theyare applied can be viewed through the medical article. It isadvantageous to view and evaluate the wound and healing thereof withoutremoval of the wound dressing to avoid unnecessary handling of the woundsite and exposure of the wound to the environment, which reduces thelikelihood of contamination, and avoids the need to cleanse the wound aswould be the case were the dressing to be removed. It is preferred thatthe dressing be both transparent and colorless so that the color of thewound, exudate, and periwound skin may also be evaluated. Preferredtransparent films for use as facing and backing layers that allow visualinspection of the wound site include polyurethane films such as thoseavailable under the trade designation ESTANE from B.F. Goodrich,Cleveland, Ohio; elastomeric polyesters such as those available underthe trade designation HYTREL from E.I. duPont deNemours & Co.,Wilmington, Del.; and, polyether block amides such as those availableunder the trade designation PEBAX from Elf Altochem North America,Philadelphia, Pa. Other useful films are those described in U.S. Pat.No. 4,499,896 (Heinecke); U.S. Pat. No. 4,598,004 (Heinecke); and U.S.Pat. No. 5,849,325 (Heinecke et al).

While the facing layer can be attached to the wound by means other thana pressure sensitive adhesive on its surface, it is preferred to usesuch an adhesive. The presence of the adhesive of the facing layernormally reduces the moisture vapor permeability of the facing layer.Therefore it is preferred that the facing layer is adhesive coated priorto adding a plurality of perforations to the layer. The wound exudatetherefore can readily pass through a perforated adhesive coated facinglayer. Preferably, both the facing and backing layers are precoated withan adhesive layer to both facilitate bonding of the backing layer to thefacing layer (forming a pouch), and bonding of the facing film to thewound site.

The facing layer is normally attached to the wound site by means ofadhesive which can be continuous or pattern coated. The preferredadhesive which can be used with the wound dressings of present inventionare the normal adhesives which are applied to the skin such as thosedescribed in U.S. Pat. No. Re. 24,906 (Ulrich), particularly a copolymerof 96% iso-octyl acrylate units and 4% acrylamide units and a copolymerof 94% iso-octyl acrylate units and 6% acrylic acid units. Other usefuladhesives are those described in U.S. Pat. No. 3,389,827 that compriseblock copolymers having three or more polymer block structures having ageneral configuration -A-B-A- wherein each A is a thermoplastic polymerblock with a glass transition temperature above room temperature (i.e.,above about 20° C.) having an average molecular weight between about5000 and 125,000 and B is a polymer block of a conjugated diene havingan average molecular weight between about 15,000 and 250,000. Additionalexamples of useful adhesives are acrylic adhesives such as iso-octylacrylate/N-vinyl pyrrolidone copolymer adhesives and crosslinkedacrylate adhesives such as for example those described in U.S. Pat. No.4,112,213 (Waldman). Inclusion in the adhesive of medicaments is usefulfor enhancing wound healing and the inclusion of antimicrobial agentssuch as iodine is useful for preventing infection.

The adhesive may optionally be a microsphere adhesive with low traumaproperties as described in U.S. Pat. No. 5,614,310 (Delgado et al.); afibrous adhesive with low trauma properties as described in U.S. Pat.No. 6,171,985 B1 (Joseph et al.); or have especially good adhesion towet skin, such as the adhesives described in U.S. Pat. No. 6,198,016 B1(Lucast et al.), and International Publication Nos. WO 99/13866 and WO99/13865; multilayered adhesives as disclosed in U.S. Pat. PublicationNo. 2001/0051178 A1 (Blatchford et al.). A particularly preferredadhesive includes 15 wt-% acrylic acid, 15 wt-% methoxypolyethyleneoxide 400 acrylate, 70 wt-% isooctyl acrylate, prepared according toExample 1 of U.S. Pat. No. 5,849,325 (Heinecke et al.).

The adhesive may be chosen to be permeable to water or wound exudate, orthe adhesive may be pattern coated on the front surface of the wounddressing (i.e. the surface in contact with the wound site, whether it isthe front surface of the facing or backing layers) so as to not impedethe flow of exudate to the gel layer, i.e. the adhesive may be coated atthe periphery of the wound dressing. Alternatively the adhesive layermay be perforated as described for the facing film to provide a fluidpath for the exudate. A release liner may be attached to the adhesivelayer for ease of handling. Examples of release liners are liners madeof or coated with polyethylene, polypropylene and fluorocarbons andsilicone coated release papers or polyester films. Examples of thesilicone coated release papers are POLYSLIK S-8004, 83 pound (135.4g/m²) bleached silicone release paper supplied by H.P. Smith Co.,Chicago, Ill., and 80 pound (130.5 g/m²) bleached two-sided siliconecoated paper (2-80-BKG-157) supplied by Daubert Chemical Co., Dixon,Ill.

A wound dressing of the present invention may also include a frame thatallows the dressing to be more easily applied to the wound. The framesare made of a relatively rigid material that maintains the shape of thedressing during handling and application to the wound site. The frame isgenerally releasably adhered to the back surface of the backing film andis removed after application of the wound dressing. Suitable frames aredescribed in U.S. Pat. No. 5,531,855 (Heinecke et al.) and U.S. Pat. No.5,738,642 (Heinecke et al.).

An optional patterned surface may be imparted to the gel material byconventional molding techniques. Alternatively, a desired pattern may beimparted using an embossing technique. Examples of such techniques aredescribed in International Publication No. WO 01/60296 A1.

EXAMPLES

The following examples are offered to aid in understanding of thepresent invention and are not to be construed as limiting the scopethereof. Unless otherwise indicated, all parts and percentages are byweight.

These examples are merely for illustrative purposes only and are notmeant to be limiting on the scope of the appended claims. All parts,percentages, ratios, etc. in the examples and the rest of thespecification are by weight, unless noted otherwise. Solvents and otherreagents used were obtained from Sigma-Aldrich Chemical Company;Milwaukee, Wis. unless otherwise noted.

Table of Abbreviations Abbreviation or Trade Designation DescriptionJEFFAMINE Amine terminal PEO/PPO, commercially available XTJ-506 fromHuntsman Corp, Houston, TX JEFFAMINE Amine terminal PEO/PPO,commercially available M-2070 from Huntsman Corp, Houston, TX PEOPolyethylene oxide PPO Polypropylene oxide PEO/PPO- Prepared asdescribed in the Preparative Examples silane section. PEG- Prepared asdescribed in the Preparative Examples methacrylate- section. silaneNALCO 2326 Nanosilica particle sol with 16% by weight particles of 5nanometers average particle size commercially available from NalcoChemical, Naperville, IL. NALCO 2327 Nanosilica particle sol with 40% byweight particles of 20 nanometers average particle size commerciallyavailable from Nalco Chemical, Naperville, IL. SILQUESTMethacryloxypropyl trimethoxysilane commercially A-174 available fromOSi Specialties, Inc., Danbury, CT. M-PEG 400 A Methoxypolyethyleneglycol 400 acrylate from Osaka Organic Chemical Industry, Ltd., Osaka,Japan M-PEG 454 A Methoxypolyethylene glycol 454 acrylate available fromSigma-Aldrich, Milwaukee, WI. M-PEG Methoxypolyethylene glycol 300methacrylate MA 300 available from Sigma-Aldrich, Milwaukee, WI. HEMAHydroxyethyl methacrylate MAA-PEG Methacrylated polyalkylene oxideprepared according to U.S. Pat. No. 7,005,143, Preparative Example 1.IRGACURE Photocatalyst commercially available from Ciba 2959 SpecialtyChemicals, Tarrytown, NY. IRGACURE Photocatalyst commercially availablefrom Ciba 819 Specialty Chemicals, Tarrytown, NY. PET film Poly(ethyleneterephthalate) release liner film with a thickness of 40 micrometers.

Test Methods Absorbency

The absorbency of each exemplary composition was determined by weighinga 2×2 centimeter square of the cured composition, with a thickness ofapproximately 1.1 millimeters and recording this as “dry weight”. Thesample was then immersed in approximately 200 milliliters of 0.9 weightpercent aqueous NaCl for 24 hours, removed from the solution and theexcess liquid was allowed to drip off of the sample for 1 minute. Thesample was again weighed and this weight was recorded as “wet weight”.The absorbency of each sample was calculated as the increase in sampleweight, expressed as a percentage of the dry weight, according to theformula:

[(wet weight−dry weight)/dry weight]*100=absorbency

Thermogravimetric Analysis

The Thermogravimetric Analysis (TGA) was performed using a TAInstruments TGA 2950 and heating the sample to 550° C. at a rate of 10°C./minute under a nitrogen purge in an aluminum pan. The wt % silica wasthen determined based on the residual mass after heating.

Compression Testing

Compression testing was done on the swollen films using a TA instrumentsDMA Q800. The films were immersed in approximately 200 milliliters of0.9 weight percent aqueous NaCl for 24 hours, removed from the solutionand tested immediately. The samples tested were 8 millimeters indiameter and approximately 1 millimeter thick. Samples C5 and 21-23 werethree millimeters thick. The samples were strained at a rate of 5% perminute until failure. All of the samples that did not fail were stoppedwhen the load limit of the instrument was reached. The secant moduluswas determined at 0.08 MPa by dividing this stress by the correspondingstrain for the sample.

Preparative Example 1 Preparation of PEO/PPO-Silane 1

In a glass reaction vessel JEFFAMINE XTJ-506, (50.32 grams) was heatedto 40° C. and 3-isocyanatopropyl triethoxysilane (10.33 grams) wasadded. After shaking for 10 minutes, a yellow solution was formed thatslowly crystallized into a waxy solid of the PEO/PPO-silane.

Preparative Example 2 Preparation of PEO/PPO-Silane 2

In a glass reaction vessel JEFFAMINE M-2070, (100.00 grams) and3-isocyanatopropyl triethoxysilane (12.37 grams) was added. Aftershaking for 30 minutes, a yellow solution of the PEO/PPO-silane 2 wasformed.

Preparative Example 3 Preparation of PEG-Methacrylate-Silane

In a glass reaction vessel poly(ethylene glycol (400) monomethacrylate(Polysciences) (50.00 grams), 3-isocyanatopropyl trimethoxysilane (19.51grams), triethylamine (9.60 grams) and butylated hydroxytoluene (0.01grams) were added. The contents were heated at 45° C. for three hours.Residual triethylamine was removed under vacuum to yield the product.

Example 1

To Nalco 2326 (100.00 grams) a solution of PEO/PPO-silane 1 (21.6 grams,0.018 moles), SILQUEST A-174 (4.48 grams, 0.018 moles) and1-methoxy-2-propanol (150 grams) was added slowly over 15 minutes. Themixture was heated to 80° C. with mechanical stirring for 24 hours.After cooling, M-PEG 400 A (30.00 grams) was added and the mixture wasplaced under vacuum to remove solvents. A clear, transparent solutionwas obtained (68.91 grams).

Example 2

To Nalco 2326 (150.00 grams) a solution of SILQUEST A-174 (13.43 grams,0.054 moles) and 1-methoxy-2-propanol (175 grams) was added slowly over15 minutes. The mixture was heated to 80° C. with mechanical stirringfor 24 hours. After cooling, HEMA (34.6 grams) was added and the mixturewas placed under vacuum to remove solvents. A clear, transparentsolution was obtained (87.5 grams).

Example 3

To Nalco 2327 (100.00 grams) a solution of PEO/PPO-silane 2 (30.00grams, 0.015 moles), SILQUEST A-174 (2.46 grams, 0.010 moles) and1-methoxy-2-propanol (150 grams) was added slowly over 15 minutes. Themixture was heated to 80° C. with mechanical stirring for 24 hours.After cooling, M-PEG 300 MA (80.0 grams) was added and the mixture wasplaced under vacuum to remove solvents. A clear, transparent solutionwas obtained (154.2 grams).

Example 4

To Nalco 2327 (50.00 grams) a solution of PEO/PPO-silane 2 (15.00 grams,0.007 moles), SILQUEST A-174 (1.23 grams, 0.005 moles) and1-methoxy-2-propanol (75 grams) was added slowly over 15 minutes. Themixture was heated to 80° C. with mechanical stirring for 24 hours.After cooling, M-PEG A 400 (40.0 grams) was added and the mixture wasplaced under vacuum to remove solvents. A clear, transparent solutionwas obtained (79.1 grams).

Example 5

To Nalco 2326 (50.00 grams) a solution of PEG-methacrylate-silane (14.33grams, 0.007 moles) and 1-methoxy-2-propanol (75 grams) was added slowlyover 10 minutes. The mixture was heated to 95° C. with mechanicalstirring for 24 hours. After cooling, 30 grams of the above solution andM-PEG A 400 (7.5 grams) were mixed and the mixture was placed undervacuum to remove all solvents. A clear, transparent solution wasobtained

Examples 6-22 and Comparative Examples C1-C5

For Examples 6-23 and Comparative Example C1-C4, a series of films wereprepared by mixing the components listed in Table 1 in a vial. Themixtures were purged with nitrogen for 10 minutes and then poured into asquare TEFLON mold (39×39×1.5 millimeters). A layer of PET film was thenplaced on top of the film. This construction was irradiated for 30minutes using a Sylvania F40/350 BL lamp (available from OSRAM SYLVANIA,Danvers, Mass.) with the sample approximately 2.5 centimeters from thelamp. The absorbency of each exemplary composition was determined byusing the Absorbency test method listed above. The Absorbency test andthe data are listed in Table 8. Additionally samples were testedaccording to the TGA Analysis and Compression Testing test methodslisted above, the data are listed in Table 8.

TABLE 1 Weight of Particle sample with M-PEG 400 A from M-PEG Exam-Example 1 400 A HEMA IRGACURE IRGACURE ple (grams) (grams) (grams) 2959(g) 819 (g) C1 0 6.50 3.50 0.050 0.050 6 1.00 5.93 3.07 0.050 0.050 72.00 5.36 2.64 0.050 0.050 8 3.00 4.79 2.21 0.050 0.050 9 4.00 4.22 1.780.050 0.050

TABLE 2 Weight of Particle sample with HEMA from M-PEG Exam- Example 2454 A HEMA IRGACURE IRGACURE ple (grams) (grams) (grams) 2959 (g) 819(g) C2 0 6.50 3.50 0.050 0.050 10 1.00 5.85 2.60 0.050 0.050 11 3.003.90 0.45 0.050 0.050

TABLE 3 Weight of Particle sample with HEMA from M-PEG Example 2 MAA-PEG454 A HEMA IRGACURE IRGACURE Example (grams) (grams) (grams) (grams)2959 (g) 819 (g) C3 0 2.00 6.00 2.00 0.050 0.050 12 1.00 1.91 5.73 1.360.050 0.050 13 3.00 1.73 5.19 0.43 0.050 0.050

TABLE 4 Weight of Particle sample with M-PEG 400 A M-PEG from Example 1MAA-PEG 454 A HEMA IRGACURE IRGACURE Example (grams) (grams) (grams)(grams) 2959 (g) 819 (g) C4 0 2.00 6.50 1.50 0.050 0.050 14 1.00 1.905.68 1.43 0.050 0.050 15 3.00 1.70 4.03 1.28 0.050 0.050

TABLE 5 Weight of Particle sample with M-PEG 300 MA from M-PEG Example 3MAA-PEG 454 A HEMA IRGACURE IRGACURE Example (grams) (grams) (grams)(grams) 2959 (g) 819 (g) 16 1.00 1.91 5.66 1.44 0.050 0.050 17 3.00 1.733.98 1.30 0.050 0.050

TABLE 6 Weight of Particle sample with M-PEG 400 A from M-PEG Example 4MAA-PEG 454 A HEMA IRGACURE IRGACURE Example (grams) (grams) (grams)(grams) 2959 (g) 819 (g) 18 1.00 1.90 5.68 1.43 0.050 0.050 19 3.00 1.704.03 1.28 0.050 0.050

TABLE 7 Weight of Particle sample with M-PEG 400 A from M-PEG Exam-Example 5 454 A HEMA IRGACURE IRGACURE ple (grams) (grams) (grams) 2959(g) 819 (g) C5 0 5.6 2.7 0.04 0.04 20 1.00 5.00 2.70 0.04 0.04 21 2.003.00 1.62 0.03 0.03 22 3.00 2.50 1.35 0.03 0.03

TABLE 8 Weight % Compression Secant Modulus Exam- Silica by Test Stressat at 0.08 MPa ple Absorbency TGA Test failure (MPa) (Pa) C1 691 0 0.121.09 × 10⁵  6 505 3.3 Did not fail 1.46 × 10⁵  7 379 5.5 Did not fail2.17 × 10⁵  8 273 8.9 Did not fail 3.32 × 10⁵  9 207 11.2 Did not fail5.60 × 10⁵ C2 515 0 0.13 1.44 × 10⁵ 10 379 2.9 Did not fail 1.78 × 10⁵11 115 11.9 Did not fail 5.10 × 10⁵ C3 478 0 Did not fail 1.92 × 10⁵ 12387 2.2 Did not fail 2.63 × 10⁵ 13 194 7.6 Did not fail 5.72 × 10⁵ C4532 0 Did not fail 1.66 × 10⁵ 14 433 2.5 Did not fail 2.28 × 10⁵ 15 2546.9 Did not fail 3.98 × 10⁵ 16 467 2.3 Did not fail 1.75 × 10⁵ 17 3456.9 Did not fail 2.66 × 10⁵ 18 479 1.8 Did not fail 1.95 × 10⁵ 19 4285.6 Did not fail 2.00 × 10⁵ C5 471 0 0.07 0.08 MPa stress not achieved21 456 1.8 0.13 1.95 × 10⁵ 22 267 5.1 Did not fail 4.43 × 10⁵ 23 198 7.6Did not fail 6.50 × 10⁵

1. A cured composition comprising the reaction product of: a) 1 to 20parts by weight of a surface modified nanoparticle component havingethylenically unsaturated groups and hydrophilic poly(alkylene oxide)groups, wherein the average particle size of said nanoparticlecomponent, prior to surface modification, is 20 nanometers or less; andb) 80 to 99 parts by weight of a monomer component comprising: amonofunctional poly(alkylene oxide) free-radically polymerizablemacromonomer having a poly(alkylene oxide) moiety, and wherein the partsby weight of a) and b) are based on 100 parts by weight of the totalcured composition.
 2. The cured composition of claim 1 wherein themonofunctional poly(alkylene oxide) free-radically polymerizablemacromonomer is of the formula:R⁶-Q-(CH(R¹)—CH₂—O—)_(m)—(CH₂—CH₂—O—)_(n)—R² wherein R⁶ is a anethylenically unsaturated polymerizable group; R¹ is a (C₁-C₄) alkylgroup, R² is H or R¹, Q is —O—, —S— or —NR²—, n is at least 5, m may be0, n+m is at least 5, and the mole ratio of n:m is at least 2:1.
 3. Thecured composition of claim 2, wherein m is at least 1 and the mole ratioof n to m (n:m) is greater than 2:1.
 4. The cured composition of claim 2where R⁶ is selected from the group consisting of:

wherein R² is H or R¹, R¹ is a C₁ to C₄ alkyl, R⁵ is an aromatic group,aliphatic group, alicyclic group, or combinations thereof, W is analkylene or poly(alkylene oxide) group, and r=2-10.
 5. The curedcomposition of claim 1 wherein the surface modified nanoparticlescomprise inorganic nanoparticles modified by a first surface modifyingagent having an ethylenically unsaturated group and a second surfacemodifying agent having poly(alkylene oxide) groups.
 6. The curedcomposition of claim 1 wherein the nanoparticles are selected from thegroup consisting of silica, alumina, tin oxide, iron oxide, zirconia,vanadia, titania; and combinations thereof.
 7. The cured composition ofclaim 1 wherein the average particle size of said nanoparticlecomponent, prior to surface modification, is less than 10 nanometers. 8.The cured composition of claim 5 wherein said first surface modifyingagent is of the formula Y—R³—Si—(OR⁴)_(b)(R⁴)_(3-b), wherein: R³ is acovalent bond or a polyvalent hydrocarbon bridging group, Y is anethylenically unsaturated polymerizable group, R⁴ is independently analkyl, aryl, or aralkyl group of 1 to 8 carbon atoms optionallysubstituted in available positions by oxygen, nitrogen and/or sulfuratoms; and b is 1 to
 3. 9. The cured composition of claim 5 wherein saidsecond surface modifying agent is of the formulaR²—(OCH₂CH₂—)_(n)(OCH₂CH(R¹))_(m)-Q′-R³—Si—(OR⁴)_(b)(R⁴)_(3-b), whereinQ′ is a divalent linking group; R¹ is a C₁ to C₄ alkyl group, R² is R¹or H, R³ is a covalent bond or a divalent hydrocarbon bridging group; R⁴is independently an alkyl, aryl, or aralkyl group of 1 to 8 carbon atomsoptionally substituted by catenary oxygen, nitrogen and/or sulfur atoms;n is at least 5, m may be 0, and the mole ratio of n:m is at least 2:1;and b is 1 to
 3. 10. The cured composition of claim 5 wherein the ratioof hydrophilic poly(alkylene oxide) groups to ethylenically unsaturatedgroups on the surface of the inorganic nanoparticles is 1:10 to 10:1.11. The cured composition of claim 5 wherein said first surfacemodifying agent is used in amounts sufficient to react with 10 to 90% ofthe available functional groups on the surface of the inorganicnanoparticles.
 12. The cured composition of claim 1 wherein the monomercomponent comprises: a) 30 to 80 wt. % of a monofunctional poly(alkyleneoxide) free-radically polymerizable macromonomer having a poly(alkyleneoxide) moiety; b) 5 to 40 wt. % of a polar monomer; c) 0 to 20 wt. % ofa hydrophobic monomer; d) 0 to 20 wt. % of a multifunctionalpoly(alkylene oxide) free-radically polymerizable macromonomer having apoly(alkylene oxide) moiety.
 13. The cured composition of claim 12comprising 0.1 to 20 wt. % of said multifunctional poly(alkylene oxide)free-radically polymerizable macromonomer.
 14. The cured composition ofclaim 8, wherein R³ is a poly(alkylene oxide) group.